JP6601870B2 - Forward / reverse feed AC arc welding method - Google Patents

Description

  The present invention relates to a forward / reverse feed AC arc welding method in which a welding wire feeding speed is alternately switched between a forward feeding period and a backward feeding period, and an electrode polarity is alternately switched between an electrode positive polarity and an electrode minus polarity. It is about.

  In general consumable electrode arc welding, a welding wire that is a consumable electrode is fed at a constant speed, and an arc is generated between the welding wire and a base material to perform welding. In the consumable electrode type arc welding, the welding wire and the base material are often in a welding state in which a short circuit period and an arc period are alternately repeated.

  In order to further improve the welding quality, a method has been proposed in which welding is performed by periodically repeating forward and backward feeding of the welding wire (see, for example, Patent Document 1).

  In invention of patent document 1, it is set as the average value of the feeding speed according to the welding current setting value, and the frequency and amplitude of the forward feed and reverse feeding of the welding wire are values according to the welding current setting value.

  The invention of Patent Document 2 describes an AC arc welding method in which a welding wire (electrode) is fed and welding is performed by alternately switching the electrode polarity between an electrode plus polarity and an electrode minus polarity.

Japanese Patent No. 52012266 Japanese Patent No. 5090765

  In the forward / reverse feed AC arc welding method in which the welding wire feed speed is alternately switched between the forward feed period and the reverse feed period, and the electrode polarity is alternately switched between the electrode positive polarity and the electrode negative polarity. Since the direction and the value of the feeding speed at the time of switching fluctuate every switching, there is a problem that the welding state becomes unstable.

  Therefore, an object of the present invention is to provide a forward / reverse feed AC arc welding method capable of stabilizing the welding state when the electrode polarity is switched.

In order to solve the above-described problems, the invention of claim 1
In the forward / reverse feed AC arc welding method in which the welding wire feeding speed is alternately switched between the forward feeding period and the reverse feeding period, and the electrode polarity is alternately switched between the electrode positive polarity and the electrode negative polarity, and welding is performed.
The electrode polarity is switched when the feeding speed is a specific phase ,
The specific phase is set to a phase during which the feeding speed during the normal feeding period is decelerated, or a phase where the feeding speed during the normal feeding period ends deceleration.
This is a forward / reverse feed AC arc welding method.

  According to the present invention, the electrode polarity switching timing is performed at a constant phase of the feeding speed. For this reason, in this invention, the welding state at the time of switching of electrode polarity can be stabilized.

It is a block diagram of the welding apparatus for enforcing the forward / reverse feeding AC arc welding method which concerns on Embodiment 1 of this invention. It is a timing chart of each signal in the welding apparatus of FIG. 1 which shows the forward / reverse feed AC arc welding method according to Embodiment 1 of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
FIG. 1 is a block diagram of a welding apparatus for carrying out a forward / reverse feed AC arc welding method according to Embodiment 1 of the present invention. Hereinafter, each block will be described with reference to FIG.

  The inverter circuit INV receives an AC commercial power supply (not shown) such as a three-phase 200V as an input, rectifies and smoothes the AC commercial power supply, generates a DC voltage, and controls this DC voltage according to a drive signal Dv described later. And outputs high-frequency alternating current.

  The high frequency transformer INT converts the high frequency alternating current into a voltage value suitable for welding. The secondary rectifier group D2 rectifies the converted high-frequency AC and outputs positive and negative DC voltages.

  The output polarity of the welding apparatus is switched by controlling on / off of the electrode positive polarity switching element PTR and the electrode negative polarity switching element NTR. When the electrode positive polarity switching element PTR is in the on state, the electrode has a positive polarity EP, and when the electrode negative polarity switching element NTR is in the on state, the electrode has a negative polarity EN. The reactor WL smoothes the output.

  The feed motor WM receives a feed control signal Fc described later, and feeds the welding wire 1 at a feed speed Fw by periodically repeating forward feed and reverse feed. A motor with fast transient response is used as the feed motor WM. In order to increase the rate of change of the feeding speed Fw of the welding wire 1 and the reversal of the feeding direction, the feeding motor WM may be installed near the tip of the welding torch 4. In some cases, two feed motors WM are used to form a push-pull feed system.

  The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 coupled to the feeding motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2. A welding voltage Vw is applied between the power feed tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw is conducted.

The polarity switching signal generation circuit SPN receives a polarity switching signal Spn, which will be described later, and a feed speed setting signal Fr, which will be described later, and inputs a predetermined first period after the polarity switching signal Spn has changed to a high level. The feed speed setting signal Fr changes to the Low level when the specific phase is reached, and the feed speed setting signal Fr is changed after a predetermined second period has elapsed since the polarity switching signal Spn changed to the Low level. A polarity switching signal Spn that changes to a high level when the specific phase is reached is output. As the specific phase of the feed speed setting signal Fr, one of the following three is selected and set. The specific phase when changing the polarity switching signal Spn to the Low level and the specific phase when changing to the High level may be set to different phases.
1) The specific phase is set while the feed speed setting signal Fr during the normal feed period is decelerating. That is, it is set during a period in which Fr ≧ 0 and the differential value dFr / dt <0 of the feed speed setting signal Fr.
2) The specific phase is set to a phase at which the feed speed setting signal Fr during the normal feed period starts to decelerate. That is, Fr ≧ 0 and dFr / dt is first set to a negative value.
3) The specific phase is set to a phase where the feeding speed setting signal Fr during the normal feeding period ends deceleration. That is, the phase is set such that Fr = 0 and dFr / dt <0.

  The electrode positive polarity switching element drive circuit EPD outputs the electrode positive polarity switching element drive signal Epd when the polarity switching signal Spn is at a high level. The electrode negative polarity switching element drive circuit END outputs an electrode negative polarity switching element drive signal End when the polarity switching signal Spn is at a low level. Accordingly, when the polarity switching signal Spn is at a high level, the electrode has a positive polarity EP, and when it is at a low level, the electrode has a negative polarity EN.

  The output voltage setting circuit ER outputs a predetermined output voltage setting signal Er. The output voltage detection circuit ED detects the secondary output AC voltage (output voltage E) of the high-frequency transformer INT, converts it to an absolute value, smoothes it, and outputs an output voltage detection signal Ed.

  The voltage error amplification circuit EA amplifies an error between the output voltage setting signal Er and the output voltage detection signal Ed, and outputs a voltage error amplification signal Ea. With this circuit, the welding apparatus has constant voltage characteristics. The drive circuit DV receives the voltage error amplification signal Ea, performs PWM modulation control based on the voltage error amplification signal Ea, and outputs a drive signal Dv for driving the inverter circuit INV.

  The average feed speed setting circuit FAR outputs a predetermined average feed speed setting signal Far.

  The amplitude setting circuit WFR outputs a predetermined amplitude setting signal Wfr. The frequency setting circuit SFR outputs a predetermined frequency setting signal Sfr.

  The feed speed setting circuit FR receives the average feed speed setting signal Far, the amplitude setting signal Wfr, and the frequency setting signal Sfr, and receives the amplitude determined by the amplitude setting signal Wfr and the reciprocal of the frequency setting signal Sfr. A predetermined trapezoidal wave that changes into a positive and negative shape with a period determined by a certain period setting value is a waveform in which the average feeding speed Fa for each period is shifted to the positive feeding side by a value equal to the average feeding speed setting signal Far The feed speed setting signal Fr is output. The feed speed setting signal Fr will be described in detail with reference to FIG. The waveform of the feed speed setting signal Fr may be a sine wave or a triangular wave in addition to the trapezoidal wave.

  The feed control circuit FC receives the feed speed setting signal Fr and receives a feed control signal Fc for feeding the welding wire 1 at a feed speed Fw corresponding to the value of the feed speed setting signal Fr. It outputs to said feed motor WM.

  FIG. 2 is a timing chart of each signal in the welding apparatus of FIG. 1 showing the forward / reverse feeding AC arc welding method according to the first embodiment of the present invention. (A) shows the time change of the feeding speed Fw, (B) shows the time change of the welding current Iw, (C) shows the time change of the welding voltage Vw, (D) ) Shows the time change of the polarity switching signal Spn. Hereinafter, the operation of each signal will be described with reference to FIG.

  As shown in FIG. 4D, the polarity switching signal Spn is at the low level (electrode negative polarity EN) during the period before time t17, and is at the high level (electrode positive polarity EP) during the period from time t17 to t37. During the period from time t37 to t57, the level is Low (electrode minus polarity EN), and during the period after time t57, the level is High (electrode plus polarity EP). The polarity switching signal Spn is repeated with time t17 to t57 as one cycle.

  The feed speed Fw shown in FIG. 6A is controlled to the value of the feed speed setting signal Fr output from the feed speed setting circuit FR of FIG. The feed speed setting signal Fr is an average feed for each period of a predetermined trapezoidal wave that changes into a positive / negative shape with a period that is the reciprocal of the amplitude Wf determined by the amplitude setting signal Wfr and the frequency Sf determined by the frequency setting signal Sfr. The waveform is shifted to the forward feed side by a value at which the speed Fa is equal to a predetermined average feed speed setting signal Far. For this reason, as indicated by a broken line in FIG. 5A, the average feed speed Fa is equal during both the electrode positive polarity period and the electrode negative polarity period.

  As shown in FIG. 5A, the feed speed Fw is one period from time t1 to t2, time t2 to t3, time t3 to t4, time t4 to t5, and time t5 to t6.

  As shown in FIG. 4A, the feed speed Fw is formed from a predetermined reverse feed acceleration period, reverse feed peak period, reverse feed peak value, and reverse feed deceleration period in the reverse feed period from time t1 to t14. The normal feed period from time t14 to t2 is formed from a predetermined normal feed acceleration period, a normal feed peak period, a normal feed peak value, and a normal feed deceleration period, respectively. As shown in FIG. 4D, the polarity switching signal Spn is at the low level before time t17, and therefore has the electrode minus polarity EN. For this reason, the welding current Iw shown in the figure (B) and the welding voltage Vw shown in the figure (C) become negative values. At time t17, the polarity switching signal Spn changes to the high level, so that the electrode has a positive polarity EP. For this reason, the welding current Iw and the welding voltage Vw are positive values. That is, at time t17, the electrode polarity is switched from the electrode negative polarity EN to the electrode positive polarity EP.

[Operation in the reverse feed period from time t1 to t14]
As shown in FIG. 5A, the feed speed Fw enters the reverse feed acceleration period from time t1 to t11, and accelerates from 0 to the reverse feed peak value. During this period, the short-circuit state continues. This period is electrode negative polarity EN, and Iw ≦ 0 and vw ≦ 0.

  When the reverse acceleration period ends at time t11, as shown in FIG. 5A, the feeding speed Fw enters the reverse peak period at times t11 to t13, and becomes the reverse peak value described above. At time t12 during this period, an arc is generated by the pinch force generated by reverse feeding and energization of the welding current Iw. In response to this, the welding voltage Vw suddenly increases to an arc voltage value of several tens of volts as shown in FIG. 5C, and the welding current Iw is set to the arc period thereafter, as shown in FIG. The inside gradually decreases. Since this period is the electrode negative polarity EN, Iw ≦ 0 and Vw ≦ 0.

  When the reverse feed peak period ends at time t13, as shown in FIG. 5A, the reverse feed deceleration period starts at times t13 to t14 and decelerates from the reverse feed peak value to zero. During this period, the arc period continues. Since this period is the electrode negative polarity EN, Iw ≦ 0 and Vw ≦ 0.

[Operation in the forward feed period from time t14 to t2]
As shown in FIG. 5A, the feed speed Fw enters the forward feed acceleration period from time t14 to t15, and accelerates from 0 to the forward feed peak value. During this period, the arc period remains. Since this period is the electrode negative polarity EN, Iw ≦ 0 and Vw ≦ 0.

  When the forward feed acceleration period ends at time t15, the feed speed Fw enters the forward feed peak period from time t15 to t17, as shown in FIG. At time t16 during this period, a short circuit occurs due to normal feeding. In response to this, the welding voltage Vw rapidly decreases to a short-circuit voltage value of several V as shown in FIG. 5C, and the welding current Iw is maintained during the subsequent short-circuit period as shown in FIG. Gradually increases. Since this period is the electrode negative polarity EN, Iw ≦ 0 and Vw ≦ 0.

  When the forward feed peak period ends at time t17, as shown in FIG. 5A, the forward feed deceleration period of time t17 to t2 starts, and the forward feed peak value decelerates to zero. During this period, the short circuit period continues. At time t15, the period during which the polarity switching signal Spn is at the low level is equal to the predetermined second period, but the low level is maintained until the feeding speed Fw reaches the specific phase. Here, the specific phase of the feed speed Fw is set during the forward feed deceleration period from time t17 to t2. In this figure, the specific phase is set at the start time of the forward feed deceleration period at time t17. At time t17, the polarity switching signal Spn is switched from the Low level to the High level because the period during which the polarity switching signal Spn is at the Low level is equal to or longer than the second period and the feed speed Fw is in the specific phase. Accordingly, the electrode polarity is switched from the electrode negative polarity EN to the electrode positive polarity EP. Therefore, during this period, Iw ≧ 0 and Vw ≧ 0.

  During the period from the time t2 to the time t3, the operations of the reverse transmission period and the normal transmission period are repeated. However, since the polarity switching signal Spn is at a high level, the electrode has a positive polarity EP. For this reason, Iw ≧ 0 and Vw ≧ 0.

  As shown in FIG. 5A, at the start time t34 of the forward feed acceleration period during the period of the feed speed Fw from time t3 to t4, the period during which the polarity switching signal Spn is at the high level (time t17 to t34). It becomes equal to the predetermined first period. However, the high level is maintained until the start time t37 of the forward feed deceleration period in which the feed speed Fw becomes a specific phase. As shown in FIG. 4D, at time t37, the period when the polarity switching signal Spn is at the high level is equal to or longer than the first period, and the feeding speed Fw is in a specific phase, so the polarity switching signal Spn is Switch from High level to Low level. Accordingly, the electrode polarity is switched from the electrode positive polarity EP to the electrode negative polarity EN. Therefore, Iw ≦ 0 and Vw ≦ 0 during the transition to time t37.

  As shown in FIG. 5A, at the start time t55 of the forward feed peak period in the period from the time t5 to the time t6 of the feed speed Fw, the period during which the polarity switching signal Spn is at the low level (time t37 to t55) It becomes equal to said 2nd period. However, the Low level is maintained until the start time t57 of the forward feed deceleration period in which the feed speed Fw becomes a specific phase. As shown in FIG. 4D, at time t57, the polarity switching signal Spn is low because the period during which the polarity switching signal Spn is at the low level is equal to or longer than the second period and the feed speed Fw is in a specific phase. The level switches from Low level to High level. Accordingly, the electrode polarity is switched from the electrode negative polarity EN to the electrode positive polarity EP. Therefore, Iw ≧ 0 and Vw ≧ 0 during the transition to time t57.

  In the subsequent period, the above operation is repeated.

  A numerical example of the trapezoidal wave of the feeding speed Fw is shown below. The frequency Sf = 100 Hz of the feeding speed Fw and the amplitude Wf = 60 m / min. The switching frequency of the polarity switching signal Spn is 25 Hz (period is 40 ms).

  The switching frequency of the polarity switching signal Spn is set to a value smaller than the frequency of the feeding speed Fw, and the setting range is about 50 Hz or less. The setting range of the frequency of the feeding speed is about 60 to 150 Hz.

  According to the experiments by the inventors, it has been confirmed that the welding state is stabilized by performing the switching timing to the electrode positive polarity EP and the switching timing to the electrode negative polarity EN at a constant phase of the feed speed fw. did. This is because, when the phase of the feed speed Fw at the electrode polarity switching timing is not constant, various melting states at the electrode polarity switching timing are mixed, and the welding state is unstable. On the other hand, when the electrode polarity is switched at a constant phase of the feed speed Fw, the molten state at the time of switching becomes constant and the welding state is stabilized. Further, the inventors perform welding when the electrode polarity switching timing is performed in any of the reverse feed acceleration period, the reverse feed peak period, the reverse feed deceleration period, the forward feed acceleration period, the forward feed peak period, or the forward feed deceleration period. An experiment was conducted to see if the state became more stable. As a result, it was confirmed that the welding state was further stabilized by performing the electrode polarity switching timing at a specific phase during the forward feed deceleration period.

  According to the first embodiment described above, the electrode polarity is switched when the feeding speed is the specific phase. Preferably, the specific phase is set during a period in which the feeding speed during the normal feeding period is decelerating. Preferably, the specific phase is set to a phase at which the feeding speed during the normal feeding period starts to decelerate. Desirably, the specific phase is set to a phase where the feeding speed during the normal feeding period ends deceleration. Thereby, in this Embodiment, the switch timing of electrode polarity is performed with the fixed phase of a feeding speed. For this reason, in this Embodiment, the welding state at the time of switching of electrode polarity can be stabilized.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll D2 Secondary rectifier group DV Drive circuit Dv Drive signal E Output voltage EA Voltage error amplification circuit Ea Voltage error amplification signal ED Output voltage detection circuit Ed Output voltage detection signal EN Electrode minus polarity END Electrode minus polarity switching element drive circuit End Electrode minus polarity switching element drive signal EP Electrode plus polarity EPD Electrode plus polarity switching element drive circuit Epd Electrode plus polarity switching element drive signal ER Output voltage setting circuit Er Output voltage setting signal Fa Average feed rate FAR Average feed rate setting circuit Far Average feed rate setting signal FC Feed control circuit Fc Feed control signal FR Feed rate setting circuit Fr Feed rate setting signal Fw Feed rate INT High frequency transformer INV Inverter Circuit Iw Welding current NTR Electrode marker Eggplant polarity switching element PTR Electrode plus polarity switching element Sf Feeding speed frequency SFR Frequency setting circuit Sfr Frequency setting signal SPN Polarity switching signal generation circuit Spn Polarity switching signal Vw Welding voltage Wf Feeding speed amplitude WFR Amplitude setting circuit Wfr Amplitude setting Signal WL Reactor WM Feed motor

Claims (1)

In the forward / reverse feed AC arc welding method in which the welding wire feeding speed is alternately switched between the forward feeding period and the reverse feeding period, and the electrode polarity is alternately switched between the electrode positive polarity and the electrode negative polarity, and welding is performed.
The electrode polarity is switched when the feeding speed is a specific phase ,
The specific phase is set to a phase during which the feeding speed during the normal feeding period is decelerated, or a phase where the feeding speed during the normal feeding period ends deceleration.
A forward / reverse feed AC arc welding method characterized by the above.

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